Circuit breaker



w. L. BUTLER CIRCUIT BREAKER med June 19. 1942 May 11, 1943'.

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W. L. BUTLER CIRCUIT BREAKER Filed June 19, 1942 May 111, 1943.

2 Shoots-Shoot 2 Inventor: William Lawren ce Butler;

H is Attorn y Patented May 11,- 1943' UNITED STATES PATENT OFFlCE CIRCUIT BREAKER.

William Lawrence Butler, Schenectady, N. 1., assignor to General Electric Company, a corporation of New York Application June 19, 1942, Serial No. 447,625 12 Claims. (Cl. 200-116) My invention relates to circuit breakers and particularly to a new and improved form of the upon the circuit breaker illustrated in my aiding Patent No. 2,300,202, issued October 2'1,

The principal object of my invention is to provide a simple and reliable manually operable current responsively tripped circuit breaker which is trip-free in its automatic operation and which may be easily manufactured in large quantities and at low cost.

My invention is especially useful in manually operated current responsively tripped circuit breaker which is trip-free in its automatic operation and which may be easily manufactured in large quantities and at low cost.

My invention is especially useful in manually operated current responsively tripped circuit breakers used for the connection of small motors directly across a supply source without starting resistance. dimensions and at the present time are used with motors up to two horsepower at 440 volts.

To the attainment of the foregoing and other objects, my invention is preferably embodied in the detailed construction to be hereinafter more fully described and claimed and is illustrated in the accompanying drawings in which Fig. 1 is a front view of a three-phase automatic motor starting switch embodying my invention; Fig. 2 is a sectional view taken along the line 2-2 of Fig. 1 looking in the direction of the arrows and showing the operating mechanism in its on position; Fig. 3 is a side elevation of the operating mechanism with one of the lateral supporting plates removed to show the mechanism in its manual off position; Fig. 4 is a view similar to Fig. 3 showing the operating mechanism in its automatic trip position; Fig. 5 is a view similar to Figs. 3 and 4 showing the operating mechanism in its -reset position; 6 is an exploded perspective view havingvariousparts broken away to show the automatic over'current trip mechanism and the operating Lmechanism,

-t1e operating mechanism being shown in its on position; and Fig. '7 is a se'ctionalyiew' of the current responsive tripping element.

Referring now to the drawings, my invention in the form shown comprises a circuit breaker mechanism mounted upon a base ll made of These devices are of small physical.

electrically insulating material, such as a suit- I able molded compound, the base In being seated within an external casing ll having a cover l2. The base III has an irregular shape determined by convenience in supporting the various parts of the device. The switch-actuating mechanism is borne upon a pair of supporting plates l3 and II which are secured rigidly to the base III, as by bolts l5 and i6, respectively, and extend therefrom in parallel spaced relation. the operating mechanism being mounted between the plates on suitable pivot pins extending. therebetween. A manually operable operating linkage comprises a pair of push buttons I! and I8 connected to opposite ends of a rocker arm I! which is pivotally mounted upon a pin journaled in the plates I3 and I4. The push buttons i1 and I8 are attached to slotted bars Ila and lid respectively, which engage notched ends of the arm 19 and are held in place on the rocker arm l9 by a transversely bent spring strip I911. The spring strip 19a overlies the arm l9 and is notched at its ends to engage the slotted bars Ila and Illa. This construction permits the necessary angular motion between the bars Fla and l8a and the arm l9 but prevents rattling. One side of the rocker arm I9 is connected by a link 2| to a switch-actuating lever 22 which is pivotally mounted upon a pin 23 journaled in the lateral supporting plates i3v and M. The actuating lever 22 is operated in the manner of a bell crank due to the fact that the link 2i is pivotally attached by a pin 24 to a short arm 25 extending from the side of the lever 22 opposite its pivot point 23.

As best shown at Fig. 6, a movable switch member 26 is mounted as a floating lever and is of irregular shape for the accomplishment of a plurality of functions which will appear here-f inafter. Fundamentally, the lever 26 comprises, a pair of substantially parallel end portions 2L; and 28 and an offset intermediate portion 29:; having a camming surface 30 and notch 2| formed on the lower edge thereof for coopera-' tion with a pin or roller 22 flxed to the actuating lever 22. In order that the floating lever 20 and the actuating lever 22 shall be interlockingly engaged at all times and for certain other purposes to be hereinafter more fully described, the. actuating lever 22 is also provided at its upper end with a second pin or roller 33 engagea'ble 5 with a shoulder 34 and second camming surface 34a on the upper edge of the floating lever 25. The end portion 21 of the floating lever 20 is provided with a downturned latching portion 38 to which is rigidly attached a transverse latching dog and pivot pin 36 which is slidably and pivotally supported in a pair of curved slots 3! in the lateral supporting plates l3 and I4. The member 36 is normally held in fixed position and serves as a pivotal support for the end 2? of the floating lever 26. The floating lever is normally biased to a switch-opening posit on against a fixed stop pin 260 by a compression spring 261) and is engaged intermediate its ends by the actuating lever 22 to move it to a switchclosing position. The spring 2617 is disposed between the free end 28 of the floating lever 26 and one end of the rocker arm l9, thereby simultaneously to bias the floating lever to a switch-,

opening position and the rocker arm l9 and actuating lever 22 to an oil position. To retain the free end of the lever 26 in mid-position between the supporting plates I3 and M, a centering pin 260 is attached to the free end 28 of the lever 26.

The free end 28 of the floating lever 26 is fitted as a tongue into a slot formed in the upper end of a T-shaped slidable link 38. The link 38 is preferably formed of rigid insulating material and comprises the slotted portion loosely attached to the floating lever 26 and a transverse arm slotted at three points 39, 40, and 4| for the reception of resilient contact-carrying members.

I at Fig- 2.

.As shown at Figs. 1 and 2, each fixed contact 46 is mounted upon a conducting strip 46a one end of which projects into a recess 48 in the base i0 and the other end of which is mechanically and electrically connected to a terminal 49. The opposite terminals 5|] of the breaker are electrically connected to the fixed ends of the resilient contact-carrying members by means of a jumper 5| of Fig. 2 for the centerphase and through current responsive tripping mechanisms generally designated as 55 for each outside phase.

It will be understood that each of the two outside phases of the three-phase switch are provided with a current responsive tripping mechanism 55. Each of these mechanisms includes an electric heater 56 connected in series circuit relation between the contact strips 42 and 144 and the breaker terminals 50, as will be more particularly described hereinafter. Since the current responsive tripping mechanisms in both outside phases are identical, only one such mechanism will be described in detail. A single latching mechanism designated generally as 56 is provided intermediate the lateral supporting plates l3 and I4 in connection with the single centrally mounted floating lever operating mechanism. The latching mechanism 58 is adapted to be independently operated by either current responsive tripping mechanism 55, as will appear more clearly hereinafter.

Referring now particularly to Figs. 6 and 7, the current responsive tripping mechanism is supported upon a generally L-shaped metallic base 66 which is preferably channel-shaped in cross section, One leg of the channel-shaped support 66 lies along the movable contact strip 42 and the other leg of the member 66 extends 42 and is provided at its ends with a flange 60a. 1 Bolted to the flange 60a and extending substantially in alignment with the upstanding leg of the support 60, I also provide a current-conducting and supporting plate, 6|. The supporting structure is completed by an L-shaped angle.

place the supporting, structure described in the preceding paragraph, an L-shaped current-conducting strap 63 may be connected between thecontact member42 and the flange 60a. As shown, one leg of the conductive strap 63 lies along the contact strip 42 between the strip 42 and the channel-shaped support 60. The members 42, 60, and 63 are all welded together;

By means of a small ofiset spring strip 64 attached to thechannel-shaped support 60, a U- shaped current responsive actuating element is adjustably supported in'parallel spaced relation with respect to the upstanding leg of the supporting structure 60, 6|. The actuating element comprises an L-shaped mounting strip 65 and a thermo-responsive bimetallic strip 654:. Thus the U-shaped thermo-responsive actuating element 65, 65a is pivotally mounted at its bight, and the normal position of the bimetallic strip 65a is determined by the position of the mounting strip 65 with respect to the fixed base structure 60, 6|. To determine the position ofthe mounting strip 65, I provide a pair of adjustable bolts 66 and 61 for varying the spacing between the upper or free end of the mounting strip 65 and the adjacent portion of the supporting plate 6|.- The bolt 66 passes through the current-conducting supporting plate 6| and the connected supporting bracket 62 into threaded engagement with the upper end of the mounting strip 65. The bolt 61 threadingly engages the supports 6| and 62 and extends into only abutting engagement with the mounting strip 65, thereby to determine a' minimum spacing between the mounting strip and the support 6|.

As shown in Figs. 6 and '7, the electric heater 5.6 has one end connected to the current-conducting support 6| and extends down between the legs of the U-shaped actuating element 65, 65a. sothat itis in intimate heat-conducting relation with respect to the bimetallic strip 65a. It will be understood that the other end of the electric heater 56 is connected directly to the breaker terminal 50, so that current is conduct'ed'from the contact member 42 to the terminal so through a path comprising the conducting strap 65, the current-conducting support 6|, and. the electric heater 56.

They bifurcated bracket 62 serves pivotally to support an overcenter trip lever 16, one arm of which is engaged by the bimetallic strip 65a and the opposite armof which is arranged to engage the tripping element of the latch mechanism 56. As indicated at Fig. 6, the bifurcated arm of the bracket 6| has attached thereto, as by welding on the side adjacent the breaker operating mechanism, a thin, flat, U-shaped plate II, the

sht of which extends across the base of the bifurcated legof the bracket 6| and the arms of which extend in parallel relation with the arms of the bracket. The arms of the plate Ii are wider than those of the bracket 6i so that they overoi the bearing plate ii and a transverse strap I6 on the lever 19.

Since each outside phase of the breaker is provided with a current responsive tripping mechanism ll of the type described above, there is a trip lever 16' positioned on each side of the breaker operating mechanism, each lever having alatch arm extending through an opening 16 in the adjacent lateral supporting plate I! or ll. This is best illustrated at Figs. 1 and 6. As clearly illustrated ,by the broken linegprojection in Fig. 6, the inwardly extending arms of the gagement with the trip lever 92 and simultaneously to bias the trip lever 92 to a latch-releasing position with respect to the floating lever 26. I have also shown a small cantilever spring iiii carried by the lever 92 and passing loosely through the slot 91. This spring engages the base of the slot 91 in resetting operation only for a purpose which will be described-hereinafter.

Referring now particularly to Fig. 6, the operation of my new and improved circuit breaker will be clear. At Fig. 6 the mechanism is shown in the manual closed position. In this position trip levers 16 are positioned to engage and independently to operate a pivoted latch member or latch lever 90 forming part of the latching mechanism 66. The latch lever 90 is welded to a pivot pin. II which is journaled in the side supporting plates II and il. The latch lever 96 is arranged to hold in latching position a second pivoted latch member or' trip lever 92 which is likewise supported in the plates I I and II by a pivot pin 99 to which it is attached as by welding. The trip lever 92 is provided with a detent 94 for latching engagement with the dog 36 of the floating lever 26. This construction is best shown at Fig. 6.

When the latch lever 90 and trip lever 92 are in latching position, they lie in substantially parallel spaced relation, and to retain the trip lever 92 in latching position it is provided with an arm 96 formed at its ends into a tongue 96 having at least two contiguous portions of different widths. As shown at Fig. 6. the tongue 96 isformed .by providing a reduced section between'the body of the ton ue and its outer ext'remlt'ythef reduced section having two conitiguous portions of different widths. The outer extremity of the tongue'serves as a locking bar for preventing complete disengagement of the tongue with a cooperating slot in the latch lever 9,9,an'd serves also as a camming member. in reset operation as will be more fully described hereinafter. The slot in the latch lever 96 is indicated by the reference numeral 91 and. for cooperation with the two contiguous reduced portions.

of the tongue 96, the slot 91 is formed to provide two icontiguo'us portions of corresponding widths.

the narrowest portion ofthe slot being adapted to receivethe narrowest section of the tongue,

and the wider portion of the slot being adapted, to receive the wider reduced section of the,

tongue. The latching shoulder between the two contiguous portions of the slot 91 is located adjacent a slightly oflset shoulder portion of the latch lever 90 arranged to be engaged by the err-.-

the pivot 'pin and latching dog 26 is held at the base of the slots 81 by engagement of the detent .96 with the latching dog, while the free end 26 of the floating lever and the slidable link 86 are held in raised position by engagement of the pin 32 on the actuating lever 22 with the notch ii at the lower end of the camming surface 30 of the floating lever 26. In arriving at this position the flbating lever 26 was raised slightly beyond its manual closed position before the pin 3i fell into slot 22. Such overtravel of the operating mechanism is permitted by the resilience of the contact members 42, 69., and 64. In the position shown in Fig. 6, the pin Si is held in frictional latching engagement with the slot 22 by means of the compression spring 26b as well as by the spring force of the contact-carrying members 62, 43, and 44. which are slightly deformed in the closed position of the switch. In this position the compression spring 26b also biases the rocker arm l9 and the actuating lever 22 to, the "oiP position, but movement of the actuating lever 22 to the off" position is prevented by friction catch comprising the pin 32 and the notch ii. The compression spring 26b itself a ds in making this friction catch effective in so far as it aids in forcing the pin 92 into the slot 9|.

The contacts may be opened manually by depressing the push button it to rotate the rocker arm i9 in a clockwise direction about its pivot point 29 to the position shown at Fig. 3. By this movement the link 2i is constrained to exert an upward force upon the short crank arm 25 of the actuating lever 22, thereby to force the pin 92 out of the slot 3i and to rotate the actuating lever 22 in a clockwise d rection about its pivot point 29, as viewed in the drawings. until the pin 99 at the upper end of the lever 22 engages the upper camming surface a at the end 21 of the floating lever 26. During this retractive movement of the actuating lever 22 the free end 26 of the floating lever 26 is moved bv the spring 26b toward a circuit-opening position as the camming surface 36 rides along the pin 22. The mechanism is shown in its manual open position at Fig. 3.

Manual closing operation of the switch is simplvtbe opposite of the opening operation described immediately above. For manual closing the push button I! is depressed. to cause the tremity of the tongue as for a purpose which will appear hereinafter. A tension spring I66 is, connected between the latch lever 90; and the trip lever 92 on opposite sides of their p vot po nts. so that both levers are biased for clockwise rotation, as viewed in the drawings, thereby to bias the latch lever 96 toward and into latchingenactuating lever 22 to pivot in a counterclockwise direction, thereby to raise the floating lever 26 to its circuit-closing position by camming action of the pin 32 along thev camming surface 30.

Assuming now that the mechanism is in the closed position shown at Figs. 2 and 6, an automatic tripping operation upon the occurrence of anexcessive current may be traced. The tripped position of the mechanism is shown at Fig. 4. Upon the occurrence of a predetermined excessive current the heat generated in the electric heater 56 first deforms the bimetallic strip 65a. and causes its free end to move the trip lever slowly in a counterclockwise direction, as

- viewed in Fig. 6. As soon as the spring 13 is carried overcenter, the trip lever 10 continues its movement with a snap action under the influence of the overcenter spring 13 and brings that arm of the lever 10 which extends through the lateral To reset the breaker mechanism after an automatic tripping operation such as that described above, the rocker arm l9 must be moved beyond its manual open position by depression of supporting plate l3 into engagement with the free end of the latch lever 96 with a hammer blow, thereby to move the lever 90 in a counterclockwise direction as viewed at Fig. 6. counterclockwise movement of the latchlever 90 brings the I narrow portion of the slot 91 into juxtaposition with respect to the narrowest reduced section of the'tongue 96 and at the same time applies a certain amount of additional tension to the latch 'the push button I8. The reset position of'the mechanism is shown at Fig. 5, and by comparison of Figs. 4 and 5 it may be seen that the clockwise rotation of the rocker arm l9 in resetting operation forcibly raises the'link 2| to rotate the actuating lever 22 in a clockwise direction. Such. clockwise rotation of the actuating lever 22 effects a clockwise rotation of the floating lever 26 about the stop pin 260. by reason of the pressure of the pin 33 against the shoulder 34. As the latching dog and pin 36 moves downwardly in the slots 31 and the normally spring I09. As soon as the tongue 96 is released by movement of the slotted latch lever 90, the

, trip lever 92 is free to rotate about its pivot pin noted that the force exerted by the compression spring 261) tending to rotate the floating lever 26 about the pin 32 also tends to raise the end 21 of the floating lever and thus pulls upward on the detent 94 and assists in rotating the trip lever 92 in a clockwise direction.

Upon disengagement of the detent 94 from the latching-dog 36, the floating lever 26 rotates about the pin 32 on' the actuating lever 22 under the influence of the main spring 26b. Such rotation causes the free end 28 of the floating lever to move downwardly into engagement with the fixed stop pin 26a carrying with'it the slidable link 38, thereby to open thebreaker contacts. may now be clearly observed from Fig. 4, when the floating lever is in engagement with the fixed stop pin 261;, the biasing force of the movable switch contact members 42, 43, and 44 which formerly retainedlthe pin 32 in the slot 3| is no longer present. The biasing force of the compressionspring 26b is' also considerably diminished due to its extension. Furthermore, the free end 28 of the floating lever 26 has taken up such a position that the notch 32 is, in asen'se, opened up, so that it no longer offers any considerable frictional resistance to displacement of the pin 3| from the notch and along the camming surface 39. Theref ore the upward force.

exerted by the compression spring 26b upon "the rocker arm l9 raises the link 2| and turns the actuating lever 22 in a clockwise direction until the pin 33 comes into engagement with the shoulder 34 on the upper edge of the floating lever 26. By this movement the pin 32 is released from the notch3l and the pin 33. serves as an upper stop for the normally flxedend 21 of the floating lever 26. From Fig. 4'itmay now be observed that in the trippedposition the actufixed end 21 of the floating lever 26 approaches its normallatched posistion, the pin 33 slides ofi of the slightly inclined shoulder 34 and rides along the top camming surface 340 of the floating lever while it continues to force a the -end 21 of the floating lever. downwardly.

During this movement the projecting end 35 of the floating lever engages 'the arm 95 of the trip lever 92 and rotates the trip lever about its pivot pin 93 in a counterclockwise direction, as viewed at Fig. 5, until the tongue'96 of the trip lever 92; comes adjacent the wider portion of the slot .91 in the latch lever 96. When the tongue reaches this position, which is the normal latched position of the latch members, the spring I00 rotates the latch lever 90 clockwise so that the widerreduced portion of the tongue 96 falls into the wider portion of the slot 91 and the detent 94 rengages thedog 36. To fully reset the mechanism, however, the button l8 must be still further depressed to rotate the trip lever 92 counterclockwise beyond its normal latched position to the reset position of Fig. 5. In moving to the position of Fig. 5, the wide end portion of the tongue 96 engages an oilset portion of the latch lever 90 formed to provide an-inclined shoulder H3. The shoulder H3 now serves as a camming surface positively to rotate the latch lever 90 in a clockwise direction beyond its normal latched position. As shown at Fig. 5. this overtravel of the member-90 causes it to engage the tripping arm of the. trip-freelever 10, thereby to move the trip lever 16 back overcenter and reset the current responsive tripping mechanism 55. The overtravel of the lever 92 causes the spring IN to engage the base of the slot 91 thereby to apply an additional return force to the lever 92. It will be understood of course that such resetting of the mechanism 55 may be efl'ectedonly if the bimetallic strip 65 has cooled and returned to its normal position.

' Upon release of the push button [8 the latch ating lever 22 and the rocker arm l9 take up positions intermediate their manual on and ofi positions. However, the rocker arm I9 is only loosely held in the tripped position so that no harm would come to an operator in attempting to retain the operating linkage in its manual "on position while the overcurrent trip mechthe pin 32 can not be displaced from the notch 3|, the breaker contacts will be opened. These features constitute trip-free! operation.

spring I09, aided by the spring IOI, rotates both the members 99 and 92 in a clockwise direction.

through a small angle to their normal latched positions until the tongue 96 again engages the shoulder adjacent the contiguous portions of different width of the slot 91 as shown at Fig. 3. This last small movement of the trip lever 92 raises the normally fixed end 21 of the floating lever 26 so that the pin 36 is slightly removed from the lower end o the slots 31. The compression spring 26b then brings the latching dog and pin 36 into engagement with the detent 94.j In moving back to the position of Fig. 3, the floating lever 26 engages the pin 33 on the actuating lever 22 and moves the actuating lever and the rocker arm l9 back to their manual open position ofFig. 3. All the parts are now fully reset as shown at Fig. 3 and prepared for manual operation to close the breaker tothe positions shown at Figs. 2 and 6..

While I have described but a single. preferred embodiment of my invention, many modifications will occur to those skilled in the art. For example, while I have illustrated my invention as applied to a three-phase motor starting switch provided with two overcurrent trips for three-phase protection, it will be understood that my operating and matching mechanism may be used to operate any desired number of switch contacts and may be combined with any desired number of my independent overcurrent trip mechanisms. I therefore wish to have it understood that I intend in the appended claims to cover all such modifications as fall within the true spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States, is:

'1. A push button operated circuit breaker comprising cooperating switch contacts, a floating lever having a first end connected to move one of said contacts, means for slidably and pivotally suporting said lever at at least one end, a manually operable operating linkage comprising a pivotally mounted actuating lever slidably and interlockingly engaging said floating lever intermediate its ends and a' push button actuated rocker arm pivotally mounted intermediate its ends at a fixed point and linked with said actuating lever to control the movement thereof, re-

leasable latch means for normally retaining the other end of said floating lever in a position flxed with respect to said fixed point, said floating lever providing friction catch means arranged to engage said actuating lever for retaining said floating lever in a contact-closing position, a spring connected between said floating lever and a movable position of said operating linkage to bias said floating lever to a contact-opening position and said linkage to an ofl position while biasing said friction catch means into engagement with said actuating lever, and means responsive to the current traversing said contacts for releasing said latch means.

2. A push-button operated circuit breaker comprising cooperating switch contacts, a floating lever having one end connected to move one of said contacts and formed to provide a camming portion intermediate the ends thereof, means for slidably and pivotally supporting the other end of said floating lever, an actuating lever pivoted at a fixed point and slidably and interlocklngly engaging said camming portion, said camming portion including a friction catch for retaining said actuating lever in a contact-closing position, a push button actuated rocker arm pivoted intermediate its ends at a second fixed point and having one end mechanically connected to said actuating lever to control movement of said actuating lever, releasable latch means for normally retaining said other end of said floating lever in a fixed position with respect to said fixed points, spring means operatively connected between said floating lever and said rocker arm for biasing said actuating lever and said rocker arm to an on position and biasing said floating lever to a contact-opening position and into engagement with said friction catch, and means responsive to the current-traversing said contacts for releasing said releasable latch means.

3. A push button operated circuit breaker comprising cooperating switch contacts, a floating lever for moving one of said contacts, said floating lever having a normally fixed end and a free "end connected by an intermediate portion providing a camming surface, a pin and slot connection for slidably and pivotally supporting said normally fixed end of said floating lever, re-

.button actuated rocker arm, having one end connected to said actuating lever, said actuating lever providing means intermediate its ends for interlockingly engaging said intermediate portion of said floating lever, spring means connected between said manualiy operable operating linkage and said floating lever for biasing said linkage to an off position and said floating lever to a contact-opening position, and means associated with said floating lever for retaining said actuating lever in an on position against the bias of said spring means thereby to retain said floating lever in a contact closing position.

4. A push button operated circuit breaker comprising a fixed contact, a resiliently mounted movable contact, a pair of slotted lateral supporting plates, a floating lever having a free end connected to move said movable contact and a normally fixed end spaced from said free end and joined thereto by an onset intermediate portion providing a camming surface, a pin attached to said normally fixed end of said floating lever and arranged for slidable and pivotal engagement with said lateral supporting plates, stop means for limiting movement of said free end of said floating lever, an actuating lever having one end pivotally mounted at a fixed point in said supporting plates, said actuating lever having a laterally extending arm and providing means intermediate its ends for interlocking engagement with said intermediate portion of said floating lever, a manually operable push button actuated rocker arm pivotally mounted at its center in said supporting plates, a linkage connecting one end of said rocker arm to said laterally extending arm of said actuating lever, current responsive latch means for releasably restraining said normally fixed end of said floating lever against sliding movement, a main spring connected between said floating lever and said rocker arm to bias said actuating lever and said rocker arm to an ofl position and to bias said floating lever to a contact-opening position, and a friction catch for releasably retaining said actuating lever in an on position against the bias of said main and said resilientspring, both said main spring ly mounted contacts supplying pressure to said friction catch to retain said floating lever in a contact-closing position against the bias of said main spring.

5. A push button operated circuit breaker comprising a support, a flxed.contact mounted upon said support, a floating lever having one end slidably and pivotally mounted upon said support, current responsive latch means for normally restraining sliding movement of said one end of said floating lever, stop means for limiting movement of the other end of said floating lever, a movable contact operatively associated with said other end of said floating lever, an actuating lever pivotally mounted upon said support and engaging said floating lever intermediate its ends to rotate said floating lever about said one end a thereby manually to engage said contacts, a push button actuated rocker arm pivotally mounted at its center upon said support and having one end mechanically connected to said actuating lever for manual control of said actuating lever, and biasing means connected between said one end of said floating lever and said one end of said rocker arm normally to bias said floating lever to a switch-opening position and to bias said slidably and pivotally to engage said slotted support, stop means for limiting movement of the other end of said floating lever, current responsive latch means for normally restraining sliding movement of said one end of said floating lever, a resiliently mounted movable contact operatively connected to the other end of said floating lever, said floating lever intermediate the ends thereof being formed by upper and lower camming surfaces, an actuating lever pivotally mounted at a fixed point upon said support,

means associated with said actuating lever for engaging said lower camming surface to rotate said floating lever about said one end for manually engaging said contacts, a push button actuated rocker arm pivotally mounted at its center upon said support and having one end mechanically connected to said actuating lever to control movement of said actuating lever, a biasing spring connected between one end of said floating lever and one end of said rocker arm to bias said floating lever to a contact-disengaging position and said rocker arm to an off position, said spring being operable upon release of said latch to rotate said floating lever about its point of engagement with said actuating lever to disengage said contacts regardless of the position of said rocker arm, and means associated with said actuating lever to engage said upper camming surface for rotating said floating lever about said stop means to reset said latch means.

7. An automatic circuit breaker comprising a support, cooperating switch contacts, a movable switch member for moving one ofsaid contacts, a trip lever pivotally mounted upon said support and being provided at one side of its pivot point with a detent normally engaging said switch member, a projecting tongue attached to said trip lever and formed to provide contiguous portions of different widths, a latch lever pivotally mounted upon said support and having a portion on one side of its pivot point ofiset to provide a camming shoulder, said latch lever provided with a slot having contiguous portions of different widths to form a latching said. trip lever and said latch lever being interlockingly engaged for cooperation of corresponding portions of said tongue and said slot, said tongue being provided with an end portion wider than the widest portion of said slot for retaining said levers in interlocking engagement and for cooperation with said camming shoulder, a tensaid latch lever in opposition to said spring thereby to release said trip lever, thermal means responsive to the current passing through said contacts for actuating said overcenter lever, and means associated with said switch member to move said end portion of said tongue into engagement with said camming shoulder thereby to reset said trip lever, said latch lever, and said overcenter lever.

8. An automatic circuit breaker comprising a support, cooperating switch contacts, a movable switch member for moving one of said contacts, a trip lever pivotally mounted upon said support and having a detent arranged to engage said switch member, a projecting arm connected to said trip lever and extending at substantially right angles thereto, said projecting arm being provided with' an extending tongue having two contiguous portions of difierent widths .and a transverse end portion wider than either of said contiguous portions, a latch lever pivotally mounted upon said support and extending in substantially parallel spaced relation to said trip lever, said latch lever having a slot comprising two contiguous portions of different widths corresponding to said contiguous portions of said tongue and forming a latching shoulder therebetween, said projecting arm extending between said trip lever and said latch lever and said tongue being interlockingly engaged with said slot, said latch lever being also provided with an offset portion forming a camming shoulder positionedto shoulder therebetween,

sionspring connected between said one end oi said latch lever and the other end or said trip lever thereby to bias said latch lever to secure said trip lever and to bias said trip lever to release said detent, an overcenter lever for actuating be engaged by said end portion of said tongue positively to move said latch lever toward said trip lever, a tension spring interconnecting said latch lever-and said trip lever on opposite sides of their pivot point to bias said latch lever to secure said trip lever in latching position and to bias said trip lever todisengage said detent, 1

overcenter spring means responsive to the current passing through said switch contacts for moving said latch lever away from said trip lever in opposition to said spring thereby to disengage the wider portion of said tongue from said latching shoulder and permit said spring to actuate said trip lever to release said switch member, and means associated with said switch member for engaging said projecting arm to actuate said trip lever against the bias of said spring thereby to reengage said detent and to engage said camming shoulder for positively moving said latch lever to reset said overcenter spring means.

9. An adjustable snap-action thermo-responsive device comprising a support, anjovercenter toggle lever mounted upon said support, a U-shaped actuating element having one leg formed of thermo-deformable material, said leg having its free end positioned to engage said toggle lever when deformed upon the application of heat thereto, resilient means for connecting the bight of said U-shaped actuating element to said support, andmeans for adjustably positioning the other leg of said actuating element with respect to said support thereby to control the setting of said thermo-responsive device.

10. An adjustable snap-action thermo-responsiv device comprising an L-shaped support, an overcenter toggle lever pivotally mounted upon one leg of said support, a, U-shaped actuating element including at least one leg tormed of a strip of bimetallic material, said bimetallic leg being deformable upon the application of.heat thereto to change the normal spacing between its free endand the-other leg of said U-shaped actuating element and to engage and move said overcenter lever, means for resiliently mounting said U-shaped actuating element at its bight upon the other leg of said support so that said actuating element extends in substantially parallel spaced relation with said first leg of said support, and means for adjustably positioning the free end of said other leg of said actuating element with respect to said support.

11. An adjustable snap-action thermo-responsive device comprising an L-shaped support, a-

bracket extending from a first leg ofsaid sup- .port in a plane substantially perpendicular to both legs of said support, an overcenter toggle lever pivotally mounted upon said bracket, a U-shaped actuating element comprising an L-shaped mounting strip permanently connected to a strip of bimetallic material, a cantilever spring strip for resiliently attaching said U-shaped actuating element at its bi'ght to the other leg of said L-shaped support in such a position that said mounting strip extends in' substantially parallel spaced relation to said first leg of said support, said bimetallic strip being positioned to engage and actuate said overcenter lever when deformed by the application of heat thereto, and an adjusting bolt for varying the spacing between the free end of said mounting strip and said first leg of said support thereby to change the setting of said thermo-responsive device.

12. A circuit breaker comprising a pair of cooperating switch contacts, a movable switch member for moving one of said contacts, a latch member normally engaging one end of said movable switch member, a pivoted arm for moving said latch member to disengage said switch m'ember, a support providing means for pivotally supporting said am, a U-shaped actuating element having a rigid leg and a leg formed 01 a strip or bimetallic material, 'said bimetallic leg having its free end positioned to engage said arm when deformed by the application of heat thereto, resilient means for connecting said U-shaped actuating element at its bight to said support, means for adjustably positioning said rigid leg of said actuating element with respect to said support, and an electric heating element positioned between the legs of said U-shaped actuating element and connected to carry a current proportional to the current traversing said contacts thereby to heat said bimetallic strip in accordance with the magnitude oi! said last ,named current.

WILLIAM LAWRENCE BUTLER.

CERTIFICATE OF CORRECTION.

Patentno. 2,518,987. I y 1 9 43 WILLIAM LAWRENCE BUTLER.

It is herehycertified that error appears in'the printed specification of the abcw'e nunibered' patentreqairing carrectionas follows: huge I}, first 4 column, lines 17-21 inclusive, strike out the following paragraph invention is especially useful in manually operated ,.current responsively tripped circuit Breakerwhich i s tripfree in its automatic operation and which may be easily manufactfired in large quantities and at low cost."

page 5, first column, line #0, for "position" read' -portionand that I the 'saidiLetters Patentshould be read Vflth this correction therein that the same may conform to the record of the case in the Patent Office,

- si ned and sealed this 22nd day of June, A. b.1915.

. Henry Van Arsdale, (Seal) Acting Commissioner of Patents.

was No. 2,318,987

CERTIFICATE OF CORRECTION.

May 11,1915. WILLIAM LAwREncE BUTLER.

It is herehycertified that error appears in'the printed specification of the above numberedpatentreqniring correcti ones follows: Page first column, lines 17-21 inclusive, strike out the following paragraph ."Iiy invention is especially use'iul in manually operated current responsively tripped circuit breaker which is tripfree in its automatic operation and which mey be essily manufactfired in large quantities and at low cost."

page 5, first column, line 11.0,fdr "position" read -portion f and that the said Letters Patentshould be read vgith this correction therein' that thesame may confonnto the record of the case in the Patent Office,

Signed and sealed this 22nd day of June, A. b.4915.

Henry Van Arsdale (Seal) Acting Commissioner of Patents. 

